.\"	$OpenBSD: PEM_read.3,v 1.1 2016/11/28 17:55:26 schwarze Exp $
.\"	OpenSSL 99d63d46 Oct 26 13:56:48 2016 -0400
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.Dd $Mdocdate: November 28 2016 $
.Dt PEM_READ 3
.Os
.Sh NAME
.Nm PEM_write ,
.Nm PEM_write_bio ,
.Nm PEM_read ,
.Nm PEM_read_bio ,
.Nm PEM_do_header ,
.Nm PEM_get_EVP_CIPHER_INFO
.Nd PEM encoding routines
.Sh SYNOPSIS
.In openssl/pem.h
.Ft int
.Fo PEM_write
.Fa "FILE *fp"
.Fa "char *name"
.Fa "char *header"
.Fa "unsigned char *data"
.Fa "long len"
.Fc
.Ft int
.Fo PEM_write_bio
.Fa "BIO *bp"
.Fa "const char *name"
.Fa "char *header"
.Fa "unsigned char *data"
.Fa "long len"
.Fc
.Ft int
.Fo PEM_read
.Fa "FILE *fp"
.Fa "char **name"
.Fa "char **header"
.Fa "unsigned char **data"
.Fa "long *len"
.Fc
.Ft int
.Fo PEM_read_bio
.Fa "BIO *bp"
.Fa "char **name"
.Fa "char **header"
.Fa "unsigned char **data"
.Fa "long *len"
.Fc
.Ft int
.Fo PEM_get_EVP_CIPHER_INFO
.Fa "char *header"
.Fa "EVP_CIPHER_INFO *cinfo"
.Fc
.Ft int
.Fo PEM_do_header
.Fa "EVP_CIPHER_INFO *cinfo"
.Fa "unsigned char *data"
.Fa "long *len"
.Fa "pem_password_cb *cb"
.Fa "void *u"
.Fc
.Sh DESCRIPTION
These functions read and write PEM-encoded objects, using the PEM type
.Fa name ,
any additional
.Fa header
information, and the raw
.Fa data
of length
.Fa len .
.Pp
PEM is the binary content encoding first defined in IETF RFC 1421.
The content is a series of base64-encoded lines, surrounded by
begin/end markers each on their own line.
For example:
.Bd -literal -offset indent
-----BEGIN PRIVATE KEY-----
MIICdg....
\&... bhTQ==
-----END PRIVATE KEY-----
.Ed
.Pp
Optional header line(s) may appear after the begin line, and their
existence depends on the type of object being written or read.
.Pp
.Fn PEM_write
writes to the file
.Fa fp ,
while
.Fn PEM_write_bio
writes to the BIO
.Fa bp .
The
.Fa name
is the name to use in the marker, the
.Fa header
is the header value or
.Dv NULL ,
and
.Fa data
and
.Fa len
specify the data and its length.
.Pp
The final
.Fa data
buffer is typically an ASN.1 object which can be decoded with the
.Fn d2i_*
function appropriate to the type
.Fa name ;
see
.Xr d2i_X509 3
for examples.
.Pp
.Fn PEM_read
reads from the file
.Fa fp ,
while
.Fn PEM_read_bio
reads from the BIO
.Fa bp .
Both skip any non-PEM data that precedes the start of the next PEM
object.
When an object is successfully retrieved, the type name from the
"----BEGIN <type>-----" is returned via the
.Fa name
argument, any encapsulation headers are returned in
.Fa header ,
and the base64-decoded content and its length are returned via
.Fa data
and
.Fa len ,
respectively.
The
.Fa name ,
.Fa header ,
and
.Fa data
pointers should be freed by the caller when no longer needed.
.Pp
The remaining functions are deprecated because the underlying PEM
encryption format is obsolete and should be avoided.
It uses an encryption format with an OpenSSL-specific key-derivation
function, which employs MD5 with an iteration count of 1.
Instead, private keys should be stored in PKCS#8 form, with a strong
PKCS#5 v2.0 PBE; see
.Xr PEM_write_PrivateKey 3
and
.Xr d2i_PKCS8PrivateKey_bio 3 .
.Pp
.Fn PEM_get_EVP_CIPHER_INFO
can be used to determine the
.Fa data
returned by
.Fn PEM_read
or
.Fn PEM_read_bio
is encrypted and to retrieve the associated cipher and IV.
The caller passes a pointer to a structure of type
.Vt EVP_CIPHER_INFO
via the
.Fa cinfo
argument and the
.Fa header
returned via
.Fn PEM_read
or
.Fn PEM_read_bio .
If the call is successful, 1 is returned and the cipher and IV are
stored at the address pointed to by
.Fa cinfo .
When the header is malformed or not supported or when the cipher is
unknown or some internal error happens, 0 is returned.
.Pp
.Fn PEM_do_header
can then be used to decrypt the data if the header indicates encryption.
The
.Fa cinfo
argument is a pointer to the structure initialized by the previous call
to
.Fn PEM_get_EVP_CIPHER_INFO .
The
.Fa data
and
.Fa len
arguments are those returned by the previous call to
.Fn PEM_read
or
.Fn PEM_read_bio .
The
.Fa cb
and
.Fa u
arguments make it possible to override the default password prompt
function as described in
.Xr PEM_read_PrivateKey 3 .
On successful completion, the
.Fa data
is decrypted in place, and
.Fa len
is updated to indicate the plaintext length.
.Pp
If the data is a priori known to not be encrypted, then neither
.Fn PEM_do_header
nor
.Fn PEM_get_EVP_CIPHER_INFO
need to be called.
.Sh RETURN VALUES
.Fn PEM_read
and
.Fn PEM_read_bio
return 1 on success or 0 on failure.
The latter includes the case when no more PEM objects remain in the
input file.
To distinguish end of file from more serious errors, the caller
must peek at the error stack and check for
.Dv PEM_R_NO_START_LINE ,
which indicates that no more PEM objects were found.
See
.Xr ERR_peek_last_error 3
and
.Xr ERR_GET_REASON 3 .
.Pp
.Fn PEM_get_EVP_CIPHER_INFO
and
.Fn PEM_do_header
return 1 on success or 0 on failure.
The
.Fa data
is likely meaningless if these functions fail.
.Sh SEE ALSO
.Xr d2i_PKCS8PrivateKey_bio 3 ,
.Xr ERR_GET_LIB 3 ,
.Xr ERR_peek_last_error 3
